The inventive disclosures contained herein pertain to the protection of building surfaces, especially subterranean walls and floor under slabs, from water penetration.
Prefabricated waterproofing panels or sheets using natural water absorbing materials such as bentonite clay have been disclosed in U.S. Pat. Nos. 3,186,896, 3,445,322, and 4,467,015 and used for structural waterproofing. Water activates the clay material's characteristics. The clay material is not stable over time and will eventually wash away.
Water drainage is another component of a waterproofing system. Water drainage is used sometimes in combination with the waterproofing mechanism. Separate drainage devices are disclosed in U.S. Pat. Nos. 3,888,087 and 4,490,072. To inhibit clogging of the drainage passages by soil infiltration, a filter layer is sometimes bonded to prefabricated drain panels, as disclosed in U.S. Pat. Nos. 3,654,765; 4,574,541; 4,730,953; and 4,840,515. In U.S. Pat. No. 4,704,048, Ahlgrimm discloses the use of a filter material with enough strength to resist deformation into the drainage channels by back-fill loading.
Currently, commercial waterproofing membranes are dominated by rubberized-asphalt materials, while commercial drainage products are dominated by (a) a prefabricated, geocomposite panel having a polystyrene dimpled core, which is (b) covered on one side with a polypropylene non-woven filter fabric(s). The above-identified commercial drainage products are applied over the above-identified waterproofing membrane using an applied liquid adhesive, which represents a three-step installation process—the first step applies the waterproofing membrane; the second step applies the adhesive; and the third step applies the drainage products, in that order.
Waterproofing membranes using this application method are susceptible to imperfections from variation in the field installation of the membrane under uncontrolled or less-than-ideal conditions; these imperfections typically appear in the form of wrinkles and voids that are termed “fish-mouths” by those of ordinary skill in the art. These imperfections have the potential to degrade the waterproofing integrity of the installation, which will reduce functional reliability and therefore negatively impact structural warranties.
Furthermore, rubberized-asphalt waterproofing membranes are sensitive to the ultraviolet (UV) spectrum of light and will chemically degrade with exposure to the sun's rays, necessitating a maximum allowed time of 30 days before geocomposite drain panels must be installed. (See, e.g., 650 Membrane Technical Data Sheet, Ultraviolet Protection section, Polyguard® Products Inc.) Hence, it would be advantageous to apply such rubberized-asphalt waterproofing membranes in a controlled environment away from UV light (as well as any other potentially damaging environmental factors that are typically encountered at a construction site) so that such time constraints on the installation of geocomposite panels can be eliminated.
Still further, despite the rugged polypropylene non-woven filter fabric material, the earthen backfill must be applied with care to prevent damage to the filter material from rocks or other discrete material that can puncture or even rip the filter fabric, thereby introducing a latent defect into the installed drainage panel. Commercial horizontal drainage panels for under slab applications use void-maintaining woven laminates and sometimes woven fabrics bonded to the crush-resistant geocomposite panels; however, these are susceptible to de-bonding which would allow infiltration of poured non-hardened concrete or earth into the drainage channels.
In U.S. Pat. No. 8,039,081, Ianniello discloses a method for improving the bonding of filter material to the geocomposite panel. That disclosure, however, does not improve the protection of said filter material.
An improved drainage system structure able to resist crush and impact damage is disclosed in U.S. Pat. No. 5,263,792. In that patent, Davis teaches the limitations of filter fabric with respect to keeping the drainage channels free from clogging and other impediments; however, again, the filter material of this configuration would still be susceptible to damage from the application of earthen back-fill.
A combined waterproofing and drainage filter panel system is revealed in U.S. Pat. No. 4,943,185. In that patent, McGuckin discloses that using a captured bentonite-clay waterproofing material in conjunction with a structure for drainage and filtering. That system has structural and functional limitations, including the stability of the waterproofing material, the mass and inflexibility of the panels, the inability to ship and store the system in rolls, and the need to secure the system to the wall that is being protected using mechanical means such as nails or tacks. Those limitations conform to the current commercial waterproofing standard configuration.
After a waterproofing system has been applied, there is no real way to verify the quality of the installation, and furthermore, functional failures can only be detected after leakage has already occurred, usually through evidence of moisture or water within the protected structure itself. Still further, location of the actual leakage point is often difficult because water that has infiltrated a building may travel a good distance along a wall, behind the defeated waterproofing membrane, before actually entering the wall (aka, structure). Even further, the problem can be compounded by water damage to the foundation of the structure and to materials or items within the below-ground levels of a building. This may explain why standard warranties on existing commercial waterproofing systems are typically offered for only one year after installation and, under special conditions, for only five years after installation. These issues have created the need for improved reliability of the waterproofing installation, as well as the necessity for leakage detection before water can damage the protected structure.
For commercial structures, electrical leak-detection methods have been developed that map the electric-field potential across a conductive surface to measure the current flow to the grounded building structure along the leakage path (see, e.g., U.S. Pat. Nos. 6,331,778, and 8,566,051). To enhance leak detection, other techniques introduce a current-carrying channel external to the waterproofing barrier undergoing test, such as using an electrically conductive primer coating (see, e.g., U.S. Patent-Application Publication No. US 2014/0361796). While these methods are useful for above-ground horizontal waterproofing installations such as roofing, they do not address solving the below-ground leak detection problem. Moreover, while electrically-based methods for the detection of leaks have been developed to monitor for waste or chemical leakage from industrial containment facilities (see, e.g., U.S. Pat. Nos. 4,404,516; 4,725,785; 5,288,168; and 6,331,778), these techniques are not suited for below-grade structural waterproofing systems.
To sense the presence of water, an electrical-moisture-detection mechanism using inductive coupling between a sensor and reader, or alternatively, an electrically connected sensor and reader using direct current (DC) is revealed in U.S. Pat. No. 5,463,377, while other devices make use of tape-based or film-based sensors to detect the presence and/or location of moisture (see, e.g., U.S. Pat. No. 7,292,155 and U.S. Patent-Application Publication No. US 2012/0074967). These methods require the placement of a plurality of sensor and reader pairs in close proximity to each other, or a plurality of electrically-connected sensors switched or linked to a single reader. Furthermore, because the sensors are discrete from the monitored structure, their use requires installation after standard waterproofing materials are applied and/or to accommodate sensor placement before or during the installation of waterproofing materials, which reflects nonstandard modifications to the underlying structure itself. Commercially available hand-held moisture-sensing instruments are available such as those from Tramex Ltd.; however, both the discrete sensing mechanisms and the hand-held instrumentation, cannot be used with existing commercial below-grade structural waterproofing systems.
In the construction industry, a below-grade commercial waterproofing system installation represents situation where the costs of failure can be very high, and as such, methodologies to address and mitigate the risks are needed. For the aerospace, medical devices, automotive, and other failure-adverse fields, the FMEA (Failure Modes and Effects Analysis) method has been in use for decades as a necessary engineering tool to enhance the reliability of systems through identification of potential failure modes and then mitigating the associated risks. Many companies—in what would be considered non-critical industries such as consumer electronics—have also adopted FMEA as part of their normal design and process development cycles, because total costs are reduced by identifying potential failure modes and mitigating the risks.
Similarly, a below-grade commercial waterproofing system installation is an application where the costs of failure are often high. Unlike above-grade waterproofing applications such as roofing and decks, a latent defect within a below-grade system may not be readily detected until considerable progression of the leakage has already occurred, and the below-grade nature of the installation makes locating and correcting the problem an expensive proposition. If a building's contents such as computer infrastructure, vital, records or laboratory facilities (to name but a few) are damaged or destroyed by the water infiltration, the costs increase even more. If people become ill from the formation of toxic mold, and a structure becomes unusable to the occupants, the liability and costs can become catastrophic. With this perspective, it is surprising that risk-control methodologies such as FMEA are not used routinely in the below-grade waterproofing field despite the fact that FMEA processes are relatively simple to implement, and the benefits of FMEA have been demonstrated by over half a century of use in critical applications where failure is literally not an option.
The process FMEA, as applied to an existing current-art below-grade waterproofing system—installed on existing vertical concrete foundation walls for new-construction structures—identifies 15 potential failure modes, which will result in water infiltration into the structure. The associated risks are shown to be unacceptably high. What is needed is an alternative waterproofing system (including fabrication methodologies) that mitigates the risk down to an acceptable level.